One area of research has dealt with a consideration of various surface Ig-ligand interactions in B lymphocytes. It has been found that the phenomenon of surface capping of complexes involves the stimulation of translational motility. The role of Ca2 ion has been studied because of the probable associate of capping with contractile proteins. Capping does not require extracellular Ca2 ion. However, introduction of Ca2 ion into the cell by the use of a Ca2 ion ionophore stops capping. Also, caps already formed are dissociated if cells are treated with ionophore. We postulate that surface Ig-ligand complexes may indeed be linked to contractile proteins. A second area of research deals with the role of macrophages in immunity. A number of materials stimulatory for lymphocytes are secreted by macrophages. The macrophages are made to secrete either following uptake of particulate materials or following interaction with activated T cells. BIBLIOGRAPHIC REFERENCES: Abbas, A. K., Dorf, M. E., Karnovsky, M. J., and Unanue, E. R.: The distribution of a Ia antigens on the surfaces of lymphocytes. J. Immunol., 116:371, 1976. Schreiner, G. F., and Unanue, E. R.: Calcium-sensitive modulation of Ig capping: evidence supporting a cytoplasmic control of ligand-receptor complexes. J. Exp. Med., 143:15, 1976.